Rotation Drive Force Transmission Mechanism, Constant Velocity Universal Joint and Resin Joint Boot Constructing the Mechanism, and Method of Tightening Clamp Band for Constant Velocity Universal Joint

Abstract

A rotation drive force transmission mechanism has tripod constant-velocity joints coupled to respective ends of a shaft in opposite phase. Outer members of the tripod constant-velocity joints and portions of the shaft are covered with boots. When the large-diameter tube of each of the boots is fastened to the corresponding outer member by a first fastening band, a band crimping ratio is managed so as to fall within a predetermined range. Each of the outer members has a boot mount whose shape is selected to satisfy predetermined equations.

1 . A mechanism for transmitting a rotational drive force, comprising:
 a shaft;   a first tripod constant-velocity joint axially movably coupled to an end of said shaft; and   a second tripod constant-velocity joint axially movably coupled to another end of said shaft;   said first tripod constant-velocity joint and said second tripod constant-velocity joint being identical in structure to each other and fixed with respect to each other in opposite phase;   each of said first tripod constant-velocity joint and said second tripod constant-velocity joint comprising an outer member and a boot of synthetic resin fastened to said shaft and to said outer member by respective boot bands, said boot having a large-diameter fixing member for receiving an end of said outer member inserted therein, a small-diameter fixing member for receiving an end portion of said shaft inserted therein, and a bellows interposed between said large-diameter fixing member and said small-diameter fixing member, said bellows being progressively smaller in diameter from said large-diameter fixing member toward said small-diameter fixing member;   said bellows comprising an alternate succession of peaks and valleys;   wherein when said outer member is inserted in said large-diameter fixing member, one of said peaks which is closest to said large-diameter fixing member has a wall thickness greater than the remaining peaks.   
   
   
       2 . A mechanism according to  claim 1 , wherein:
 said outer member has a boot mount on which said boot is mounted;   said boot mount comprises an annular surface of substantially flat, said boot being mounted on said annular surface, an engaging groove defined in said annular surface, and an annular slanted surface inclined to said annular surface;   a groove bottom of said engaging groove and a point where said slanted surface starts to rise from said annular surface are spaced horizontally from each other by a distance L 2 ;   said boot has an annular ridge engaging in said engaging groove, a crest of said annular ridge and an end face of said boot are spaced horizontally from each other by a distance L 1 ; and   when the difference between said distance L 2  and said distance L 1  is represented by L (L=L 2 −L 1 ), and said annular slanted surface is inclined to said annular surface by an angle θ, said difference L (mm) and said angle θ (°) are set to values in ranges satisfying the following equations (1) through (5):
     L≦ 0.0833θ−3.4796  (1) 
     L≦− 0.0188θ+1.2353  (2) 
   θ≧ 20   (4) 
   θ≦ 60 .  (5) 
   
   
   
       3 . A mechanism according to  claim 2 , wherein said difference L (mm) and said angle θ (°) are set to values in ranges satisfying the following equations (6) through (8):
     L≦ 0.0833θ−3.4796  (6)       L≧ 0.0833θ−4.796  (7)     θ=45±1.5.  (8)   
   
   
       4 . A mechanism according to  claim 1 , wherein one of said valleys which is closest to said large-diameter fixing member has a radius of curvature greater than those of the remaining valleys. 
   
   
       5 . A mechanism according to  claim 1 , wherein said small-diameter fixing member has a band mounting slot for receiving one of said boot bands therein, and said boot has a curved portion extending from a bottom of said band mounting slot to a side wall of one of said peaks which is closest to said small-diameter fixing member, said curved portion having a radius of curvature ranging from 0.4 to 0.6 mm. 
   
   
       6 . A constant-velocity joint comprising:
 an outer member including a boot mount disposed on an end thereof; and   a boot of synthetic resin including a tubular fixing member disposed on an end thereof;   wherein said fixing member is fixed to said boot mount by mounting said fixing member on said boot mount and thereafter fastening said fixing member with a boot band;   said boot mount comprises an annular surface of substantially flat, said boot being mounted on said annular surface, an engaging groove defined in said annular surface, and an annular slanted surface inclined to said annular surface;   a groove bottom of said engaging groove and a point where said slanted surface starts to rise from said annular surface are spaced horizontally from each other by a distance L 2 ;   said boot has an annular ridge engaging in said engaging groove, a crest of said annular ridge and an end face of said boot being spaced horizontally from each other by a distance L 1 ; and   when the difference between said distance L 2  and said distance L 1  is represented by L (L=L 2 −L 1 ), and said annular slanted surface is inclined to said annular surface by an angle θ, said difference L (mm) and said angle θ (°) are set to values in ranges satisfying the following equations (1) through (5):
     L≦ 0.08330θ−3.4796  (1) 
     L≦− 0.0188θ+1.2353  (2) 
     L≧ 0.0176θ−3.372  (3) 
   θ≧ 20   (4) 
   θ≦ 60 .  (5) 
   
   
   
       7 . A constant-velocity joint according to  claim 6 , wherein said difference L (mm) and said angle θ (°) are set to values in ranges satisfying the following equations (6) through (8):
     L≦ 0.0833θ−3.4796  (6)       L≧ 0.0833θ−4.796  (7)     θ= 45 ± 1 . 5 .  (8)   
   
   
       8 . A boot of synthetic resin for use with a constant-velocity joint having an outer member, comprising:
 a large-diameter tube for receiving an end of said outer member inserted therein;   a small-diameter tube for receiving an end portion of a shaft inserted therein; and   a bellows interposed between said large-diameter tube and said small-diameter tube and being progressively smaller in diameter from said large-diameter tube toward said small-diameter tube;   said bellows comprising an alternate succession of peaks and valleys;   wherein when said outer member is inserted in said large-diameter tube, one of said peaks which is closest to said large-diameter tube has an inner wall surface spaced from an outer wall surface of an open end of said outer member, providing a space therebetween; and   said one of the peaks which is closest to said large-diameter tube has a wall thickness greater than the remaining peaks.   
   
   
       9 . A boot according to  claim 8 , wherein one of said valleys which is closest to said large-diameter tube has a radius of curvature greater than those of the remaining valleys. 
   
   
       10 . A boot according to  claim 8 , wherein said small-diameter tube has a band mounting slot for receiving a fastening band therein, and said boot has a curved portion extending from a bottom of said band mounting slot to a side wall of one of said peaks which is closest to said small-diameter tube, said curved portion having a radius of curvature ranging from 0.4 to 0.6 mm. 
   
   
       11 . A method of crimping a fastening band of a constant-velocity joint after an outer member of the constant-velocity joint is inserted in a tubular insert on an end of a joint boot and the fastening band is wound around an outer circumferential surface of said tubular insert, comprising the step of:
 managing crimping of said fastening band based on a band crimping ratio defined by the following equation (A):
   band crimping ratio (%)=(the outside diameter of the outer member+the wall thickness of the joint boot before the fastening band is crimped)/the inside diameter of the fastening band after the fastening band is crimped  (A). 
   
   
   
       12 . A method of crimping a fastening band according to  claim 11 , wherein said joint boot comprises a joint boot of synthetic resin, and said band crimping ratio is in the range from 0.16 to 1.3%. 
   
   
       13 . A method of crimping a fastening band according to  claim 11 , wherein said joint boot comprises a joint boot of rubber, and said band crimping ratio is in the range from 0.1 to 1.6%.